1. Technical Field
The present disclosure relates to controlling a switching power converter in more than one operation mode to increase the efficiency of the power converter at low-load or no-load conditions.
2. Description of the Related Arts
Increased efficiency demands placed on portable electronic devices create challenges for regulating power in low-load or no-load operation in a switching power converter. These challenges include consuming nearly no power in standby mode, while being able to quickly deliver power when the device is suddenly plugged-in.
In low-load or no-load operation, switching power converters operate at a low switching frequency represented by FSW. On the other hand, low switching frequencies make it difficult to satisfy the demands of fast dynamic load response (DLR) in switching power converters. The impact of these competing requirements may be even more apparent in the operation of a flyback power converter with a primary-side feedback switching power converter. In a primary-side feedback flyback power converter, the primary voltage feedback responds to the load change cycle-by-cycle. To regulate the output voltage switching cycle-by-switching cycle, the primary feedback voltage is typically sampled once per switching cycle. If the switching frequency becomes too low, the resulting switching period may be too long to sample information between consecutive switching cycles and result in a distorted waveform of the output voltage. On the other hand, an increase in switching frequency results in a proportional undesirable increase in power supply consumption.